Pumps that displace a fluid can come in a variety of configurations. For example, gear pumps are positive displacement (or fixed displacement) pumps, i.e. they displace a constant amount of fluid per each rotation and they are particularly suited for pumping high viscosity fluids such as crude oil but can also pump other types of fluids such as water and hydraulic fluid. Gear pumps typically comprise a casing (or housing) having a cavity in which a pair of gears are arranged, one of which is known as a drive gear, which is driven by a driveshaft attached to an external driver such as an engine or an electric motor, and the other of which is known as a driven gear (or idler gear), which meshes with the drive gear. Gear pumps, in which one gear is externally toothed and the other gear is internally toothed, are referred to as internal gear pumps. Either the internally or externally toothed gear is the drive or driven gear. Typically, the axes of rotation of the gears in the internal gear pump are offset and the externally toothed gear is of smaller diameter than the internally toothed gear. Alternatively, gear pumps, in which both gears are externally toothed, are referred to as external gear pumps. External gear pumps typically use spur, helical, or herringbone gears, depending on the intended application.
When the pumps, whether external or internal, are used in fluid pumping systems, especially closed-loop systems, fluid storage devices are typically provided in the system. The fluid storage devices can be used to store excess fluid and to release stored fluid when required by the system. For example, the volume of a closed-loop system that includes a fluid-operated cylinder (e.g., a hydraulic operated cylinder) may vary depending on whether the cylinder is being extended or retracted. This can be because of a difference in volumes between the extraction chamber and the retraction chamber of the cylinder. For example, the retraction chamber can have a smaller volume due to the piston rod. When the cylinder is retracted, a closed-loop system must account for the extra fluid and this is typically done by storing the extra fluid in a storage device. When the cylinder is extended and the volume in the system increases, additional fluid is needed to replenish the system to fully extend the cylinder. When this happens, the stored fluid in the storage device is transferred back into the system. In addition to storing and releasing fluid, storage devices can also be used to dampen pressure spikes and/or mitigate or eliminate other pressure/volume disturbances in the fluid system, e.g., due to temperature variations in the fluid system. However, conventional fluid storage devices are typically installed remotely from the pump and are connected to the fluid system using piping and/or hoses. Thus, in related art systems, the pump and storage device combination is not a compact arrangement. In addition, the piping and hoses are sources of potential contamination for the fluid system.
Further limitation and disadvantages of conventional, traditional, and proposed approaches will become apparent to one skilled in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present disclosure with reference to the drawings.